Diphosphines

ABSTRACT

The invention relates to the preparation and use as catalysts of diphosphines of the formula (I)  
                 
 
     in which  
     R is C 6 -C 14 -aryl or C 4 -C 13 -heteroaryl containing 1 to 3 heteroatoms selected from the group consisting of nitrogen, oxygen, and sulfur, wherein the aryl and heteroaryl radicals may optionally be substituted by halogen, C 1 -C 6 -alkyl, C 1 -C 6 -alkoxy, and/or trimethylsilyl, and  
     R 1  to R 4 , independently of one another, are each hydrogen, C 1 -C 10 -alkyl, C 1 -C 10 -alkoxy, F, Cl, or Br.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a process for the preparation ofracemic diphosphines, to a process for the preparation ofenantiomerically pure diphosphines, to novel enantiomerically purediphosphines, to novel intermediates for the preparation ofdiphosphines, and to catalysts that contain novel diphosphines.

[0002] A process that differs greatly from the process according to theinvention for the preparation of diphosphines is known from EP-A749,973. According to this, if the intention is to prepareenantiomerically pure diphosphines, the racemate resolution is carriedout at the stage of the phosphine oxides, i.e., for individualdiphosphines separate racemate resolutions must be carried out.Compounds different from the compounds according to the invention aredescribed in EP-A 104,375, EP-A 582,692, and EP-A 690,065. Racemateresolutions with N-benzylcinchonidinium chloride have hitherto beendescribed only for dinaphthol compounds (Tetrahedron Lett. 36, 7991(1995)).

SUMMARY OF THE INVENTION

[0003] Specifically, the present invention first relates to a processfor the preparation of racemic diphosphines of the formula (I)

[0004] in which

[0005] R is C₆-C₁₄-aryl or C₄-C₁₃-heteroaryl containing 1 to 3heteroatoms selected from the group consisting of nitrogen, oxygen, andsulfur, wherein the aryl and heteroaryl radicals may optionally besubstituted by halogen, C₁-C₆-alkyl, C₁-C₆-alkoxy, and/ortrimethylsilyl, and

[0006] R¹ to R⁴, independently of one another, are each hydrogen,C₁-C₁₀-alkyl, C₁-C₁₀-alkoxy, F, Cl, or Br,

[0007] comprising

[0008] (a) converting a phenol of the formula (II)

[0009]  in which R¹ to R⁴ have the meanings given for formula (I), intothe corresponding phenoxide using a base,

[0010] (b) reacting the phenoxide with dihalogenomethane to give aformaldehyde acetal of the formula (III)

[0011]  in which R¹ to R⁴ have the meanings given for formula (I),

[0012] (c) intramolecularly oxidatively coupling the formaldehyde acetalof the formula (III) to give a cycloheptadiene of the formula (IV),

[0013]  in which R¹ to R⁴ have the meanings given for formula (I),

[0014] (d) converting the cycloheptadiene of the formula (IV) bytreatment with an acid into a biphenyldiol of the formula (V)

[0015]  in which R¹ to R⁴ have the meanings given for formula (I),

[0016] (e) preparing the corresponding triflate from the biphenyldiol ofthe formula (V), and

[0017] (f) coupling the triflate with a secondary phosphine of theformula (VI)

HPR₂  (VI),

[0018]  in which R has the meaning given for formula (I),

[0019]  with the addition of a base and in the presence of apalladium(0), palladium(II), nickel(0), and/or Ni(II) compound, therebygiving a compound of the formula (I).

DETAILED DESCRIPTION OF THE INVENTION

[0020] In the formulas (I) to (V), R¹ and R² are preferably hydrogen andR³ and R⁴ are preferably C₁-C₅-alkoxy, fluorine, or chlorine. In theformulas (I) and (VI), R is preferably phenyl, furyl, or2-N—C₁-C₆-alkylpyrrolyl that may optionally be substituted by 1 to 3substituents from the group consisting of fluorine, chlorine,C₁-C₅-alkyl, C₁-C₆-alkoxy, and trimethylsilyl. In the formulas (I) to(V), R¹ and R² are particularly preferably hydrogen, R³ is particularlypreferably chlorine, and R⁴ is particularly preferably methoxy orethoxy. In the formulas (I) and (VI), R is particularly preferablyphenyl, 2-furyl, 2-N-methylpyrrolyl, 3,5-dimethylphenyl, 4-fluorophenyl,4-tolyl, or 3,5-dimethoxyphenyl.

[0021] In the conversion of the phenol of the formula (II) into thecorresponding phenoxide, the base that can be used is, for example, analkali metal hydride, hydroxide, or carbonate. Preference is given tosodium hydride and potassium hydride. The base is preferably used in anamount of from 0.9 to 1.5 equivalents per mole of phenol of the formula(II). Here, it is possible to work in the presence of a solvent, e.g.,in the presence of a dipolar-aprotic solvent, such as dimethylformamide,or an ether, such as diethyl ether, tetrahydrofuran, dioxane, or methyltert-butyl ether.

[0022] Suitable reaction temperatures, particularly when alkali metalhydrides are used as base, are, for example, those in the range from −20to +60° C. It is advantageous to carry out this stage under a protectivegas atmosphere. The procedure may involve, for example, initiallyintroducing the base together with the solvent and metering in thephenol of the formula (II) dissolved in the same solvent.

[0023] The phenoxide obtained does not need to be isolated. Particularlyif the process has been carried out with stoichiometric amounts ofalkali metal hydride as base, the reaction mixture that is presentfollowing reaction with the base can be further used directly.

[0024] In the reaction with the phenoxide it is possible to use, basedon one mole of phenol of the formula (II) originally used, e.g., 0.4 to0.7 mol of dihalogenomethane. Suitable reaction temperatures are, forexample, those from 0 to 80° C., particularly those from 10 to 60° C.The reaction time for the reaction with the dihalogenomethane can be,for example, 8 to 40 hours. Suitable as dihalogenomethane is, forexample, dichloromethane, dibromomethane, and diiodomethane.Diiodomethane is preferred.

[0025] The reaction mixture that is then present can be worked up, forexample, by extracting it after addition of water with a virtuallynonpolar or nonpolar organic solvent and removing the solvent from theextract. The residue that remains can, if desired, be further purified,for example, by dissolving it in an ether, in methanol, or inacetonitrile at elevated temperature, discarding the insolublecomponents, and obtaining the prepared formaldehyde acetal of theformula (III) in purified form by crystallization.

[0026] The intramolecular oxidative coupling for the preparation of acycloheptadiene of the formula (IV) can be carried out, for example, byfirst adding an organolithium compound to the formaldehyde acetal of theformula (III) and, when they have finished reacting, adding an oxidizingagent. For example, it is possible to add butyllithium dissolved in, forexample, a hydrocarbon to a solution of the formaldehyde acetal, forexample in ether, at −30 to +40° C. and leave the mixture to fully reactby after-stirring at a temperature in this range. Per mole offormaldehyde acetal, it is possible to use, for example, 2.0 to 2.2 molof organolithium compound. In general, the reaction is complete after 5to 30 hours. The oxidizing agent can then be added, for example aCu(II), Fe(III), Mn(III), or Ce(IV) compound. The oxidative coupling canalso be carried out enzymatically, e.g., with a peroxidase. Theoxidizing agent is added at, for example, −70 to −30° C., and themixture is subsequently warmed to a temperature of, for example, below50° C. Based on 1 mol of formaldehyde acetal of the formula (III) used,it is possible to use, for example, 2.0 to 2.5 equivalents of anoxidizing agent. It is advantageous to continue to after-stir thereaction mixture in conclusion, e.g., for 1 to 5 hours.

[0027] It is also possible to carry out the oxidative coupling directlyfrom the formaldehyde acetal of the formula (III) in accordance with themethods described here without converting said formaldehyde acetal intothe Li salt beforehand.

[0028] It is advantageous at least to carry out the reaction with theorganolithium compound under a protective gas atmosphere.

[0029] The treatment with an acid to convert a cycloheptadiene of theformula (IV) into a biphenyldiol of the formula (V) can be carried out,for example, with a strong mineral acid such as hydrochloric acid orsulfuric acid. For example, 5 to 15 equivalents of acid can be used permole of cycloheptadiene of the formula (IV). The procedure isexpediently carried out in the presence of a solvent, for example in thepresence of an alcohol. The treatment with the acid can be carried out,for example, in a period of from 5 to 50 hours at temperatures of from50 to 100° C. The reaction mixture can be worked up, for example,analogously to the procedure described above for the preparation offormaldehyde acetals of the formula (III).

[0030] The preparation of the triflate compound (i.e., atrifluoromethane-sulfonic ester) from the biphenyldiol of the formula(V) can be carried out, for example, by suspending the biphenyldiol ofthe formula (V) in a solvent (e.g., an aromatic hydrocarbon), adding atertiary amine (e.g. pyridine), and then metering in, for example,trifluoromethanesulfonic anhydride or trifluoromethanesulfonyl chloride,optionally dissolved in a solvent (e.g., in an aromatic hydrocarbon),and after-stirring. The metered addition and after-stirring can becarried out, for example, at 0 to 60° C. A suspension forms during thisoperation. Per mole of biphenyldiol of the formula (V), it is possibleto use, for example, 2 to 3 mol of a tertiary amine and 2 to 2.2 mol oftrifluoromethanesulfonic anhydride or trifluoromethanesulfonyl chloride.

[0031] For work-up, the reaction mixture can, for example, be washedwith water and aqueous sodium chloride solution, the organic phase thatis left behind can be dried, and the solvent can be removed, wherenecessary by stripping it off under reduced pressure. The productobtainable in this way is pure enough for the reaction with secondaryphosphines. If desired, it can be further purified, e.g., by (flash)column chromatography.

[0032] For the reaction of the triflate compound with a secondaryphosphine of the formula (VI), the base that may be used is, forexample, a tertiary amine (for example, a trialkylamine), that containsthree identical or different C₁-C₆-alkyl groups. Arylalkylamines, DABCO,“proton sponges” (e.g. 1,8-bis(dimethylamino)naphthalene) and hydrogencarbonates, such as sodium hydrogen carbonate, are also possible.Preference is given to using triethylamine or ethyl-diisopropyl-amine.The amount of base used, based on one mole of the triflate compound,can, for example, be 2 to 3 mol.

[0033] Suitable palladium(0) or nickel(0) compounds are, for examplecomplexes of the formulas (VIIa) and (VIIb),

Pd(PR′₃)₄  (VIIa)

Ni(PR′₃)₄  (VIIb)

[0034] in which

[0035] R′ is in each case C₁-C₁₀-alkyl or C₆-C₁₄-aryl, where aryl mayoptionally be substituted by halogen and/or C₁-C₆-alkyl, and where R′ ispreferably phenyl.

[0036] Also suitable as palladium(0) compound is Pd₂(dba)₃, where dba isdibenzylideneacetone. The Pd₂(dba)₃ can optionally also contain acoordinated solvent molecule, e.g., CHCl₃.

[0037] It is also possible to use a palladium(0) compound of the formula(VIIc)

Pd(L₂)   (VIIc),

[0038] in which

[0039] L is R′₂P—(CH₂)_(n)—PR′₂, diphenylphosphinoferrocenyl, or2,2′-bis-(diphenylphosphinomethyl)-1,1′-binaphthyl, where R′ has themeaning given above and n is 1, 2, 3, or 4.

[0040] Preferred compounds of the formula (VIIc) are those in which L isR′₂P—(CH₂)_(n)—PR′₂, where R′ is phenyl and n is 2, 3, or 4.

[0041] Suitable as palladium(II) compound is, for example, Pd(CH₃COO)₂,and suitable as nickel(II) compound, for example, NiCl₂ that optionallyalso contains 1 to 2 coordinated PR′₃-molecules (where R′ has the samemeaning as in the formulas (VIIa) and (VIIb)).

[0042] Preference is given to using palladium(0) compounds of theformulas (VIIa) and (VIIc) and Pd₂(dba)₃. These compounds can, ifdesired, also be prepared in situ, for example, by initially introducingpalladium diacetate into a solvent and adding the ligands in thestoichiometrically required amount or in an excess of up to, forexample, 150% of the stoichiometrically required amount.

[0043] The amount of palladium and/or nickel compounds used, based on 1mol of triflate compound, can be, for example, 0.001 to 0.1 mol.

[0044] The reaction of the triflate compound with a secondary phosphineof the formula (VI) can be carried out, for example, by initiallyproducing the palladium(0), palladium(II), nickel(0), and/or nickel(II)compound in a dipolar-aprotic solvent or preparing said compound in situin a dipolar-aprotic solvent, and then bringing it together with thesecondary phosphine of the formula (VI), the base, the triflatecompound, and optionally further solvent. It is also possible to preparea mixture as described above that contains the palladium and/or nickelcompound, to add this mixture to an initial charge of triflate compound,and then to add base, secondary phosphine of the formula (VI), andoptionally further solvent. The preparation of the mixture containingpalladium and/or nickel compounds can be carried out, for example, at−10 to +40° C., and the reaction with the triflate compound can becarried out at, for example, 20 to 160° C. The reaction of the triflatecompound can require, for example, reaction times in the range from 5 to200 hours.

[0045] Isolation and purification of the diphosphine compound of theformula (I) prepared in this way can be carried out, for example, byfirst stripping off the solvent at elevated temperature under reducedpressure, taking up the residue with toluene, passing this mixture overa silica column, taking the fraction containing the prepareddiphosphine, stripping off the toluene therefrom, dissolving the residuein dimethylformamide, and crystallizing the prepared diphosphine bylayering with methanol or dialkyl ether.

[0046] The present invention further relates to a process for thepreparation of enantiomerically pure diphosphines of the formula (VIII)

[0047] in which the symbols used have the meanings given for formula(I), and of a formula that is analogous to formula (VIII) but representsthe other enantiomer.

[0048] This preparation is carried out according to the invention likethe above-described preparation of the racemic diphosphines of theformula (I) and is additionally characterized in that the biphenyldiolof the formula (V) is subjected to racemate resolution. The racemateresolution can be carried out, for example, by crystallization using anauxiliary reagent or by chiral chromatography, e.g., according to theSMB method. Suitable auxiliary reagents for the racemate resolution bycrystallization are, for example, tartaric acid derivatives andcinchonine derivatives.

[0049] For this purpose, preference is given to using(−)-O,O′-dibenzoyl-L-tartaric acid or enantiomerically pureN-benzylcinchonidinium chloride. Per mole of biphenyldiol, it ispossible to use, for example, 0.5 to 1 mol of auxiliary reagent.

[0050] The racemate resolution can, for example be carried out byrefluxing the racemic biphenyldiol of the formula (V) together with theauxiliary reagent in a suitable solvent, e.g., a C₁-C₄-alkyl alcohol oracetonitrile for a few hours, after-stirring, filtering off theprecipitate that is present, and taking it up in a water-immisciblesolvent (e.g., a chloro-alkane, an aromatic hydrocarbon, or ethylacetate), washing with an acid, e.g., a dilute mineral acid, separatingoff the organic phase, extracting the aqueous phase with awater-immiscible solvent, and stripping off the solvent from thecombined organic phases.

[0051] The remaining preparation of enantiomerically pure diphosphinesof the formula (VIII) is then carried out as described above for thepreparation of racemic diphosphines.

[0052] The present invention further relates to enantiomerically purediphosphines of the formula (IX)

[0053] in which the radicals R″ are in each case identical and are2-furyl, 2-N-methylpyrrolyl, 4-fluorophenyl, 3,5-dimethoxyphenyl, or3,5-dimethylphenyl, and of a formula that is analogous to formula (IX)but represents the other enantiomer.

[0054] The present invention further relates to cycloheptadienecompounds of the formula (IV), to racemic and enantiomerically purebiphenyldiols of the formula (V), and to the corresponding racemic andenantiomerically pure triflate compounds accessible from thebiphenyldiols of the formula (V), wherein in the triflate compounds ineach case R¹ and R² are H, R³ is chlorine, and R⁴ is methoxy.

[0055] The racemic diphosphines of the formula (I) prepared according tothe invention and the novel enantiomerically pure (+)- and(−)-diphosphines of the formula (VIII) are suitable as ligands for thepreparation of catalysts, preferably of catalysts for hydrogenation. Theenantiomerically pure (+)- and (−)-diphosphines of the formula (VIII)are particularly suitable as ligands for the preparation ofhydrogenation catalysts for enantioselective hydrogenations.

[0056] Said ligands may, in order to be successful as hydrogenationcatalysts, be combined with metals, including in the form of metal ionsor metal complexes of elements of subgroup VIII of the Periodic Table ofthe Elements. In this connection, ruthenium, iridium, and rhodium arepreferred. Here, the ligand-metal combination may be undertakenseparately or in situ within the reaction mixture for the hydrogenation.In this connection, 0.5 to 10 mol (preferably 1 to 5 mol) of saidligands, for example, may be used per mole of metal.

[0057] The racemic diphosphines of the formula (I) can, for example, beused advantageously as ligands for palladium catalysts used in aminationreactions. Numerous intermediates for pharmaceutical and crop protectionactive ingredients are accessible by palladium-complex-catalyzedaminations. It has hitherto been known to use binaphthylphosphoruscompounds as ligands for such aminations.

[0058] Finally, the present invention also relates to catalysts thatcontain a metal, a metal ion or a metal complex of an element ofsubgroup VIII of the Periodic Table of the Elements and at least onediphosphine of the formula (IX). These catalysts preferably contain,independently of one another, ruthenium, iridium, or rhodium and 0.5 to10 mol of a diphosphine of the formula (IX) per mole of metal, metalion, or metal complex.

[0059] In the process according to the invention for the preparation ofracemic diphosphines of the formula (I), it is advantageous that a broadpalette of different ligands is accessible directly from one precursor(i.e., a compound of the formula (VI)). For example, it is readilypossible to prepare different ligands, tailored to a specific catalystproblem, that have different electronic and steric ratios.

[0060] In the process according to the invention for the preparation ofenantiomerically pure diphosphines of the formula (VIII), it isadvantageous that the phosphine radicals are introduced only after theracemate resolution. As a result, it is possible to carry out thecomplex racemate resolution for diverse diphosphines in a common initialstage and only then prepare a broad spectrum of individual diphosphines.Separate racemate resolutions for individual diphosphines can thus beavoided.

[0061] The enantiomerically pure diphosphines of the formula (IX)according to the invention have the advantage that catalysts that can beprepared therefrom are superior to other catalysts in differentreactions with regard to the enantiomer excess that is achievablefollowing their use. Ruthenium catalysts with enantiomerically pureligands according to the invention are, for example, advantageous forthe enantioselective hydrogenation of heteroaromatic ketones anditaconic acid derivatives.

[0062] The cycloheptadiene compounds, biphenyldiols, and triflatecompounds according to the invention are novel intermediates for thepreparation of novel diphosphines, from which catalysts with superiorproperties can be prepared.

[0063] The following examples further illustrate details for the processof this invention. The invention, which is set forth in the foregoingdisclosure, is not to be limited either in spirit or scope by theseexamples. Those skilled in the art will readily understand that knownvariations of the conditions of the following procedures can be used.Unless otherwise noted, all temperatures are degrees Celsius and allpercentages are percentages by weight.

EXAMPLES Example 1

[0064] Preparation of Formaldehyde bis(4-chloro-3-methoxyphenyl) Acetal(IUPAC: bis(4-chloro-3-methoxyphen-1-oxy)methane)

[0065] A solution of 100 g of 4-chloro-3-methoxyphenol in 250 ml ofdimethylformamide was slowly added dropwise to a suspension of 16.0 g ofsodium hydride (95% strength) in 300 ml of dimethylformamide under argonat 0° C. When the addition was complete, the mixture was after-stirredfor a further 1 hour at 40° C., giving a clear, yellow solution. At roomtemperature, a solution of 88.1 g of diiodomethane in 100 ml ofdimethylformamide was then slowly added dropwise. The solution wasstirred for 15 hours at room temperature, during which an orange-redsuspension gradually formed. The mixture was then stirred for a further3 hours at 50° C. 400 ml of water were added and the mixture wasextracted with 3×150 ml of methylene chloride. The combined organicphases were washed with 3×100 ml of saturated aqueous sodium chloridesolution, the organic phases were dried over sodium sulfate, and thesolvent was removed at 50° C. under reduced pressure, giving anorange-brown solid residue. This residue was dissolved in 250 ml ofmethyl tert-butyl ether at the boil, decanted off from the oily residuepresent and concentrated by evaporation until precipitation occurred.The mixture was left to crystallize first at room temperature and then,to complete the precipitation, at +4° C. The precipitate was filteredoff and carefully washed with 1:1 methyl tert-butyl ether/petroleumether. The mother liquor was concentrated by evaporation and left tocrystallize again.

[0066] Yield: 85.2 g (82% of theory)

[0067] Melting point: 110° C.

[0068] By removing the DMF prior to work-up with dichloromethane/water,it is possible to increase the chemical yield from 82 to 90%. Theintensely colored phenol oxidation products that are present can beseparated off by flash column chromatography over silica gel withdichloromethane as eluent.

[0069]¹H-NMR (CDCl₃): δ=3.87 (s, 6H, CH₃); 5.68 (s, 2H, CH₂); 6.65-6.70(m, 4H, H_(arom.)); 7.27 (d, ³J_(H-H)=8.1 Hz, 2H, H_(arom.))

[0070]¹³C-NMR (CDCl₃): δ=56.2 (CH₃); 91.4 (CH₂); 102.0 (C_(arom.));108.2 (C_(arom.)); 116.2 (C_(arom., ipso)); 130.4 (C_(arom.)); 155.7(C_(arom., ipso)); 156.5 (C_(arom., ipso))

Example 2

[0071] Preparation of2,10-dichloro-1,11-dimethoxy-5,7-dioxadibenzo[a,c]cycloheptadiene

[0072] 239 ml of a 1.6 molar solution of butyllithium in hexane wasslowly added dropwise to a solution of 60 g of formaldehyde[bis(4-chloro-3-methoxyphenyl) acetal] (IUPAC:bis(4-chloro-3-methoxyphen-1-oxy)-methane) in 100 ml of tetrahydrofuranat 0° C. under argon. When the addition was complete, the mixture wasstirred for 15 hours at room temperature, giving a yellow suspension.The reaction mixture was then cooled to −50° C., and 51.3 g of anhydrouscopper(II) chloride were added. The solution was then left to warm toroom temperature over the course of 5 hours, and then 300 ml of waterand 200 ml of methylene chloride were added. The mixture was neutralizedwith 50 ml of 2N aqueous hydrochloric acid, and then the resultingwhite-grey precipitate was redissolved by adding 300 ml of 25% strengthaqueous ammonia solution. The methylene chloride phase was separated offand the deep dark-blue aqueous phase was further extracted with 5×100 mlof methylene chloride. The organic phase was then washed a few moretimes using a total of 400 ml of saturated aqueous ammonium chloridesolution until it was only just still pale blue in color. The organicphase was concentrated somewhat by evaporation, dried over sodiumsulfate, and all of the solvent was removed, giving a brown solid, whichwas treated with 100 ml of boiling methyl tert-butyl ether. The solutionformed was decanted off from the oily residue and the solution was leftto crystallize at +4° C. The solid that precipitated out was filteredoff and the solvent was then removed from the filtrate under reducedpressure, and the residue that formed during this operation wassubjected to column-chromatographic purification with silica gel 60 andwith toluene as eluent. The yellow eluate was freed from the solventunder reduced pressure, and the residue was dissolved again in 40 ml ofboiling methyl tert-butyl ether and left to crystallize at +4° C.

[0073] Yield: 45.4 g (77% of theory)

[0074] By drying the copper(II) chloride over P₄O₁₀ at 140° C.beforehand and by using an equimolar mixture of n-butyllithium andN,N,N,N-tetramethyl(ethylenediamine) (TMEDA) it is possible to achieve avery selective aromatic coupling to give the desired product (crude NMRshows only one product).

[0075] The removal of the THF prior to work-up and an acidic work-upwith 4 N HCl has also proven advantageous.

[0076] The yield can be increased by these measures to 95% of theory.Melting point: 130° C.

[0077]¹H-NMR (CDCl₃): δ=3.60 (s, 6H, OCH₃); 5.46 (s, 2H, OCH₂O); 6.94(d, ³J=8.7 Hz, 2H, H_(arom.)); 7.43 (d, ³J=8.72H, H_(arom.))

[0078]¹³C-NMR (CDCl₃): δ=61.2 (CH₃); 102.3 (CH₂); 117.0 (C_(arom.));124.1 (C_(arom., ipso)); 124.9 (C_(arom., ipso)); 130.8 (C_(arom.));152.1 (C_(arom., ipso)); 154.4 (C_(arom., ipso))

Example 3

[0079] Preparation of 5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diol

[0080] 4 ml of concentrated aqueous hydrochloric acid were added to asuspension of 1.76 g of2,10-dichloro-1,11-dimethoxy-5,7-dioxadibenzo-[a,c]cycloheptadiene in 25ml of ethanol. The mixture was then refluxed under argon for 21 hours,the course of the reaction being monitored by means of thin-layerchromatography using methylene chloride as eluent. The resulting clear,yellow solution was admixed with 30 ml of water, extracted with 2×50 mlof methylene chloride, and washed with 2×50 ml of saturated aqueoussodium chloride solution. The organic phase was dried over sodiumsulfate and filtered, and the solvent was removed under reducedpressure. The residue was carefully triturated with cold chloroform,which was decanted off again and discarded.

[0081] Yield: 1.54 g (91% of theory)

[0082] By adding 1.5 equivalents of ethylene glycol, based on the molaramount of the acetal used, the yield can be increased to 99% of theory.

[0083] Melting point: 110° C.

[0084]¹H-NMR (CDCl₃): δ=3.66 (s, 6H, OCH₃); 5.29 (s, 2H, OH); 6.84 (d,³J_(H-H)=9.0 Hz, 2H, H_(arom.)); 7.37 (d, ³J_(H-H)=8.7 2H, H_(arom.))

[0085]¹³C-NMR (CDCl₃): δ=61.1 (CH₃); 114.4 (C_(arom.)); 115.2(C_(arom. ipso)); 119.1 (C_(arom., ipso)); 131.5 (C_(arom.)); 153.6(C_(arom., ipso)); 153.8 (C_(arom., ipso))

Example 4

[0086] Preparation of (+)-5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diol

[0087] A suspension of 22.9 g of5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diol and 16.0 g ofN-benzylcinchonidinium chloride in 110 ml of acetonitrile were refluxedfor 4 hours and then stirred for 15 hours at room temperature. Theresulting precipitate was filtered off, washed with a small amount ofacetonitrile, and dried under reduced pressure. The residue was taken upin 250 ml of ethyl acetate and extracted by shaking with 2×50 ml ofaqueous 2N hydrochloric acid. The organic phase was separated off, andthe aqueous phase was extracted again with 2×50 ml of ethyl acetate. Thecombined organic phases were washed with 4×100 ml of saturated aqueoussodium chloride solution, dried over sodium sulfate, and filtered, andthe solvent was removed under reduced pressure.

[0088] Yield: 6.77 g (30% of theory)

[0089] Enantiomer purity: 98.4 e.e.

[0090] The enantiomer purity was checked using analytical HPLC. Theeluent used was n-heptane/isopropanol 80:20

[0091] [α]_(D)=+23.6 (c=1.5; CHCl₃)

[0092] Subsequent recrystallization from chloroform gave a product withan enantiomer purity of more than 99.9% e.e.

Example 5

[0093] Preparation of (5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)bistrifluoromethanesulfonic Acid Ester

[0094] 3.4 g of (+)-5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diol weresuspended in 40 ml of toluene, and 2.5 g of pyridine were added, aclear, pale brown solution being formed within 10 min. A solution of 6.9g of trifluoromethanesulfonic anhydride in 5 ml of toluene was added tothis solution dropwise at room temperature. A flocculant precipitateformed rapidly. The mixture was stirred for 3 hours at 45° C., duringwhich an orange-colored suspension was formed. This suspension waswashed with 2×20 ml of water and then with 2×30 ml of saturated aqueoussodium chloride solution. The organic phase was dried over sodiumsulfate and filtered, and the solvent was removed at 50° C. underreduced pressure, giving an orange-colored oil. This was pure enough tobe further used directly. If desired, the oil could be further purifiedby flash column chromatography on silica gel with toluene as eluent.

[0095] Yield of oil: 5.7 g (92% of theory)

[0096]¹H-NMR (CDCl₃): δ=3.77 (s, 6H, OCH₃); 5.29 (s, 2H, OH); 7.18 (d,³J_(H-H)=9.0 Hz, 2H, H_(arom.)); 7.58 (d, ³J_(H-H)=9.0 Hz, 2H,H_(arom.))

[0097]¹³C-NMR (CDCl₃): δ=61.5 (CH₃); 117.2 (C_(arom.)); 118.3 (q, ¹J(C,F)=320 Hz, CF₃); 121.1 (C_(arom. ipso)); 127.8 (C_(arom., ipso)); 132.3(C_(arom.)); 145.9 (C_(arom., ipso)); 155.9 (C_(arom., ipso))

[0098]¹⁹F-NMR (CDCl₃): δ=74.9 (s, CF₃)

Example 6

[0099] Preparation of(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bis(diphenyl-phosphine)

[0100] 220 mg of Pd(PPh₃)₄ were added with 75 mg ofdiphenylphosphinopropane to 10 ml of dimethyl sulfoxide under argon, andthe mixture was stirred for 3 hours at room temperature, during whichtime an orange-colored suspension formed. To this suspension were added0.99 g of diphenylphosphine, 0.85 g of N,N-diisopropylethylamine, 1.00 gof(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bistrifluoromethanesulfonicacid ester, and a further 10 ml of dimethyl sulfoxide, and the clear,yellow solution was then stirred at 100° C. for 79 hours. When thereaction was complete, the solvent was removed under reduced pressure at100° C., and 10 ml of methanol were added to the residue and left tocrystallize at −25° C. The resulting fine precipitate was filtered offand washed with methanol.

[0101] Yield: 0.70 g (62% of theory).

[0102] The NMR data were identical to those given in EP-A 749,973.

Example 7

[0103] Preparation of(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bis(bis-2-furylphosphine)

[0104] 100 mg of Pd₂(dibenzylideneacetone)₃.CHCl₃ were suspendedtogether with 80 mg of diphenylphosphinopropane in 10 ml ofdimethylformamide under argon, and the mixture was stirred for 2 hoursat room temperature, during which time a clear, orange-colored solutionformed. This solution was transferred using a hollow needle to a Schlenkvessel, in which 3.40 g of(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bistrifluoromethanesulfonicacid ester had been introduced. A further 10 ml of dimethylformamide,1.56 g of triethylamine and 1.00 g of di-2-furylphosphine were added tothis solution, and the mixture was stirred for 72 hours at 100° C., afurther 1.03 g of bis-2-furylphosphine being added after 22 hours. Whenthe reaction was complete, the solvent was removed under reducedpressure at 100° C., the residue was treated for one hour with 20 ml ofdiethyl ether in an ultrasound bath, and the ethereal solution wasdecanted off from the brown, oily residue. The ether was removed underreduced pressure, and the solid that remained was taken up in 2 ml ofdimethylformamide, carefully covered with a layer of 10 ml of methanol,and left to crystallize at +4° C.

[0105] Yield: 0.85 g (24% of theory).

[0106] Melting point: 150° C.

[0107]¹H-NMR (CD₃CN): δ=3.28 (s, 6H, OCH₃); 6.37 (m, 2H, H_(arom.));6.44 (d, ³J_(H-H)=3.3 Hz, 2H, H_(arom.)); 6.48 (m, 2H, H_(arom.)); 6.65(d, ³J_(H-H)=3.3 Hz, 2H, H_(arom.)); 7.44 (dt, ³J_(H-H)=8.1 Hz,³J_(H-H)=8.1 Hz, ³J_(H-P)=1.5 Hz, 2H, H_(arom.)); 7.52 (d, ³J_(H-H)=8.4Hz, 2H, H_(arom.)); 7.64 (d, ³J_(H-H)=1.8 Hz, 2H, H_(arom.)); 7.77 (d,³J_(H-H)=1.8 Hz, 2H, H_(arom.))

[0108]¹³C-NMR (CDCl₃): δ=60.4 (CH₃); 110.6 (C_(arom.)); 110.8(C_(arom.)); 121.4 (C_(arom.)); 121.8 (C_(arom.)); 129.2(C_(arom., ipso)); 130.2 (C_(arom.)); 130.6 (C_(arom.)); 134.4(C_(arom., ipso)); 136.7 (C_(arom., ipso)); 147.4 (C_(arom.)); 149.4(C_(arom. ipso)); 150.2 (C_(arom., ipso)); 154.3 (C_(arom., ipso))

[0109]³¹P-NMR (CDCl₃) δ=−59.14

[0110] Repetition of this example using N,N-dimethylacetamide instead ofdimethylformamide gave the same product in a reaction time of 12 hours.

Example 8

[0111] Preparation of(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bis(bis-p-fluorophenylphosphine)

[0112] 100 mg of Pd₂(dibenzylideneacetone CHCl₃) were suspended togetherwith 80 mg of diphenylphosphinopropane in 10 ml of dimethylformamideunder argon, and the mixture was stirred for 2 hours at roomtemperature, during which time a clear, orange-colored solution formed.This solution was transferred using a hollow needle to a Schlenk vesselin which 3.28 g of(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bistrifluoromethanesulfonicacid ester had been introduced. To this solution were then added afurther 10 ml of dimethylformamide, 1.50 g of triethylamine and 1.25 gof bis(p-fluorophenyl)phosphine, and then the mixture was stirred for 72hours at 100° C., a further 1.75 g of bis-(p-fluorophenyl)phosphinebeing added after 23 hours. When the reaction was complete, the solventwas removed under reduced pressure at 100° C., the residue was treatedfor one hour with 10 ml of diethyl ether in an ultrasound bath, and thesolution was decanted off from the brown, oily residue. The ether wasremoved under reduced pressure, and the residue was taken up in 2 ml ofdimethylformamide, carefully coated with a layer of 10 ml of methanol,and left to crystallize at +4° C.

[0113] Yield: 0.80 g (20% of theory).

[0114] Melting point: 139° C.

[0115]¹H-NMR (CD₃CN): δ=3.35 (s, 6H, OCH₃); 6.88-7.13 (m, 14H,H_(arom.)); 7.16-7.27 (m, 4H, H_(arom.)); 7.46 (d, ³J_(H-H)=8.1 Hz, 2H,H_(arom.))

[0116]¹³C-NMR (CDCl₃): δ=60.2 (CH₃); 115.5 (C_(arom.)); 115.8(C_(arom.)); 128.7 (C_(arom., ipso)); 130.2 (C_(arom.)); 130.7(C_(arom.)); 131.7 (C_(arom., ipso)); 132.7 (C_(arom., ipso)); 134.6(C_(arom.)); 136.2 (C_(arom.)); 137.8 (C_(arom., ipso)); 154.3(C_(arom., ipso)); 161.4 (C_(arom., ipso)); 161.9 (C_(arom. ipso));164.7 (C_(arom., ipso)); 165.2 (C_(arom., ipso))

[0117]³¹P-NMR (CDCl₃) δ=−16.01

[0118]¹⁹F-NMR (CDCl₃) δ=113.6 (s, Ar—F); −112.3 (s, Ar—F)

Example 9

[0119] Preparation of(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bis(bis-3,5-dimethylphenylphosphine)

[0120] 100 mg of Pd₂(dibenzylideneacetone)₃ CHCl₃ were suspendedtogether with 80 mg of diphenylphosphinopropane in 10 ml ofdimethylformamide under argon, and the mixture was stirred for 1 hour atroom temperature, during which time a clear orange-colored solution wasformed. This solution was transferred using a hollow needle to a Schlenkvessel into which 2.70 g of(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bistrifluoromethanesulfonicacid ester had been introduced. To this solution were added a further 10ml of dimethylformamide, 1.60 g of N,N-diisopropylethylamine, and 2.43 gof bis-(3,5-dimethylphenyl)-phosphine, and then the mixture was stirredfor a total of 115 hours at 100° C., a further 0.25 g ofbis-(3,5-dimethylphenyl)phosphine being added after 75 hours, and afurther 0.32 g of bis-(3,5-dimethylphenyl)phosphine being added after100 hours. When the reaction was complete, the dimethylformamide wasremoved under reduced pressure at 100° C., and the residue was subjectedto flash column chromatography over silica gel 60 using toluene aseluent. The solvent was removed under reduced pressure, and the residuewas taken up in 2 ml of dimethylformamide, carefully coated with a layerof 8 ml of methanol, and left to crystallize at +4° C. Following removalof the 1 st precipitation fraction, the filtrate was concentrated to 1ml at 100° C. and, again after coating with methanol, left tocrystallize.

[0121] Yield: 1.50 g (42% of theory).

[0122] Melting point: 225° C.

[0123]¹H-NMR (CD₃CN): δ=2.14 (s, 12H, Ar—CH₃); 2.22 (s, 12H, Ar—CH₃);3.27 (s, 6H, OCH₃); 6.80-6.90 (m, 12H, H_(arom.)); 6.99 (d, ³J_(H-H)=9.0Hz, 2H, H_(arom.)); 7.31 (d, ³J_(H-H)=9.0 Hz, 2H, H_(arom.))

[0124]³¹P-NMR (CDCl₃): δ=−13.73

Example 10-1

[0125] Preparation of(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bis(bis-2-(N-methylpyrrolyl)phosphine)

[0126] a) Preparation of di(N-methylpyrrolyl)ethyl Phosphinite

[0127] To a solution of 38.61 g of methylpyrrole in 200 ml of diethylether were added dropwise, at 0° C., first 297.5 ml of a 1.6 molarsolution of n-butyllithium in hexane and then 35.0 g of dichloroethylphosphinite. The reaction solution was then stirred overnight at roomtemperature, and then the solvent was stripped off under reducedpressure. The residue that remained was taken up in 200 ml of petroleumether, the insoluble lithium salts were filtered off, and the solventwas stripped off from the filtrate. The residue that was formed duringthis operation was fractionally distilled.

[0128] Yield: 14.14 g (25% of theory).

[0129] Boiling point: 125-130° C. at 0.17 torr.

[0130]³¹P-NMR shift: 76.54 ppm in CDCl₃

[0131] b) Preparation of di-2-(N-methylpyrrolyl)-phosphine

[0132] To a suspension of 0.75 g of lithium aluminum hydride in 20 ml oftetrahydrofuran were added dropwise, at −70° C., 2.15 g oftrimethylchloro-silane, and the suspension was then stirred for 2 hoursat room temperature. A solution of 2.15 g of di(N-methylpyrrolyl)ethylphosphinite in 10 ml of tetrahydrofuran was then added dropwise. Thereaction mixture was stirred for 20 hours at room temperature. Thereaction mixture was then hydrolyzed with 1 g of water (until there wasno further evolution of hydrogen), the solvent was stripped off underreduced pressure, and the residue that remained was taken up inpetroleum ether. After the insoluble aluminum and lithium salts had beenfiltered off, the solvent was stripped off from the filtrate and theresidue that formed during this operation was dried under reducedpressure.

[0133] Yield: 30% of theory.

[0134]³¹P-NMR shift: −111.36 ppm in C₆D₆

[0135] c) Synthesis of the Compound Stated at the Outset

[0136] The procedure was as described in Example 6, but usingdi-2-(N-methylpyrrolyl)phosphine instead of diphenylphosphine.

[0137]¹H-NMR (CDCl₃): δ=3.04 (s, 6H); 3.26 (s, 6H); 3.66 (s, 6H);5.98-6.01 (m, 2H); 6.65 (t, 2H); 6.07-6.1 (m, 2H); 6.17 (t, 2H); 6.65(t, 2H); 6.84-6.87 (m, 2H); 6.88-6.93 (m, 2H); 7.3 (d, 2H)

[0138]³¹P-NMR (CDCl₃): δ=−58.75

Example 10-2

[0139] Preparation of(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bis(bis-3,5-dimethoxyphenyl)phosphine)

[0140] In a heat-dried Schlenk vessel with a Teflon stirrer bar, 26.4 mgof [Pd₂(dba)₃].CHCl₃ and 1.1 mg of diphenylphosphinopropane weresuspended in 3 ml of dimethylacetamide, and the mixture was stirred for30 min at room temperature, during which operation the solution becameclear and assumed a red color. This solution was transferred using ahollow needle into a Schlenk vessel in which 0.95 g of(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bistrifluoromethanesulfonicacid ester and 1.1 g of bis(3,5-dimethoxyphenyl)phosphine in 10 ml ofdimethylacetamide had been introduced. 0.64 g of diisopropylethylaminewere then added and the mixture was heated to 80° C. After 72 hours, thesolvent was removed under reduced pressure, and the residue was taken upin 2 ml of toluene and purified using flash-chromatography over silicagel with toluene as eluent. The yellowish oil that formed was taken upin diethyl ether, and the ether was then removed under reduced pressure.This gave 0.78 g of the product as a pale yellow voluminous substance.

[0141] Yield: 53% of theory

[0142]³¹P-NMR-(CDCl₃): δ=−10.61

[0143] MS (SIMS): m/z (%)=890.9 (9, M⁺), 753.0 (5, M⁺-C₈H₁₀O₂), 584.9[100, M⁺-P(C₈H₁₀O₂)₂], 448.9 [2, M⁺-P(C₈H₁₀O₂)₂—C₈H₁₀O₂], 384.93,337.05, 280.9 {19, M⁺-[P(C₈H₁₀O₂)₂]₂} 220.9 (28), 206.9 (33), 146.9(70).

Example 11

[0144] Preparation of the Catalyst(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bis(di-3,5-dimethylphenylphosphino)-bis(3,3,3-trifluoraceto)-ruthenium

[0145] 0.0431 g of (cyclooctadiene)Ru(η³-methallyl)₂ and 0.1033 g of(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bis(bis-3,5-dimethylphenylphosphine)were dissolved in 5 ml of methylene chloride, 5 ml of methanol wereadded, and then, with stirring, 21.5 μl of trifluoroacetic acid wereadded. After the mixture had been stirred for 24 hours at roomtemperature, the solvent was removed under reduced pressure and theorange-colored residue was dried for 2 hours under reduced pressure.

Example 12

[0146] Preparation of the Catalyst(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bis(bis-4-fluorophenylphosphino)-bis(3,3,3-trifluoroaceto)ruthenium

[0147] The preparation was as described in Example 11, but now using thecorresponding bis-4-fluorophenylphosphine instead of(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bis(bis-3,5-dimethylphenylphosphine).

Example 13-1

[0148] Preparation of the Catalyst(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bis-(di-2-furylphosphino)-bis(3,3,3-trifluoroaceto)ruthenium

[0149] The preparation was as described in Example 11, but now using thecorresponding bis-2-furylphosphine instead of(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bis(bis-3,5-dimethylphenylphosphine).

Example 13-2

[0150] Preparation of the Catalyst(5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl)-bis(3,5-dimethoxyphenylphosphino)-bis(3,3,3-trifluoroaceto)ruthenium

[0151] 432 mg of the product from Example 10-2 were added to a solutionof 155 mg of (cyclooctadiene)Ru(η³-methallyl)₂ in CH₂Cl₂, and themixture was stirred for 1 hour at room temperature. The solvent was thenremoved under reduced pressure. The product was formed as a dark greensolid in quantitative yield.

[0152]³¹P-NMR-(d⁴-MeOH): δ=64.22

[0153] MS (SIMS): m/z (%)=1143.2, 991.2 [12, M⁺-(CO₂CF₃)₂], 585.3[M⁺-Ru(CO₂CF₃)₂—P(C₈H₁₀O₂)₂], 147.1 (19), 132.9 (28), 73.1 (100).

Examples 14 to 20

[0154] Hydrogenations with Catalysts from Examples 11 to 13.

[0155] 20 μmol of catalyst were dissolved in 5 ml of methanol, 2.0 ml ofdimethyl itaconate, and 0.100 g of diglyme (GC standard) were added, andthe mixture was reacted with hydrogen in a glass autoclave (1 bar of H₂)or steel autoclave (70 bar of H₂). When the reaction period had expired,and optionally following decompression, a vacuum was applied to removedissolved hydrogen, and the catalyst/product solution was then analyzedby gas chromatography. The results are summarized in Table 1. TABLE 1Catalyst Reaction from Temp. Pressure time Conversion Yield ExampleExample (° C.) (bar) (h) (%) (%) TOF/h⁻¹ ee (%) Configuration 14 13-1 2370 15 99.9 100 6.6 65.5 (S) 15 13-1 50 1 1 17.0 12.2 12.3 92.5 (S) 16 1222 1 1 70 71 70 94.7 (S) 17 12 22 1 0.7 35 34 49.8 96.2 (S) 18 12 50 10.5 100 100 198 95.5 (S) 19 11 22 1 1 100 100 22 94.7 (S) 20 11 50 1 0.5100 100 >200 96.9 (S)

Examples 21 to 24

[0156] Hydrogenations with in Situ Catalyst Systems

[0157] 20 μmol of (norbornadiene)₂RhPF₆ were dissolved with in each case20 mmol of the ligands from Examples 7 to 9 in 5 ml of a solvent. Whenusing the ligand from Example 7, the solvent was methanol, and whenusing the ligands from Examples 8 and 9, the solvent was a 1:1 mixtureof methylene chloride and methanol. The mixture obtained was stirred for1 hour at 40° C., then the solvent was removed under reduced pressure,and then 5 ml of methanol were added. 2.0 mmol of dimethyl itaconate and0.100 g of diglyme (GC standard) were added, and the mixture was reactedwith hydrogen in a glass autoclave (1 bar of H₂) or steel autoclave (70bar of H₂). After the reaction time had expired, and optionally afterdecompression, a vacuum was applied to remove dissolved hydrogen, andthe catalyst/product solution was then analysed using gaschromatography. The results are summarized in Table 2. TABLE 2 ReactionTemp. Pressure time Conversion Yield Example Ligand (° C.) (bar) (h) (%)(%) TOF/h⁻¹ ee (%) Configuration 21 from 24 1 1 95 100 120 31.4 (S)Example 7 22 from 22 70 0.5 97 95 193 14.3 (S) Example 7 23 from 22 1 112 16 22 26 (S) Example 8 24a) from 22 1 1 100 100 98.5 78.3 (S) Example9 24b) from 22 100 0.5 100 100 196 58.5 (S) Example 9 24c) from 50 1000.5 100 100 >200 74.2 (S) Example 9

Examples 25 to 28

[0158] Hydrogenations with the Catalyst from Example 13-2

[0159] In a heat-dried glass autoclave (a steel autoclave was used inExample 27) charged with argon, a solution of 0.32 g of dimethylitaconate, 0.024 g of the catalyst from Example 13-2, 0.1 g of diglyme,and 5 ml of methanol was added and then 1 bar (in Example 27 70 bar) ofhydrogen was fed in. Then, at the temperature given in Table 3, themixture was vigorously stirred for 30 min. Then, to remove the hydrogen,a sample was taken to determine the conversion (GC), the mixture thatremained was subjected to flash distillation, and the enantiomer excessin the distillate was determined.

[0160] In Example 28, 0.64 g of dimethyl itaconate were used. Detailsare given in Table 3. TABLE 3 Temp. Pressure Conversion Example (° C.)(bar) (%) TOF/h⁻¹ ee (%) 25 22 1 99.9 138 92.4 26 40 1 99.7 >200 92.4 2722 70 99.7 >200 55.6 28 22 1 38.3 136 91.2

What is claimed is:
 1. A process for the preparation of racemicdiphosphines of the formula (I)

in which R is C₆-C₁₄-aryl or C₄-C₁₃-heteroaryl containing 1 to 3heteroatoms selected from the group consisting of nitrogen, oxygen, andsulfur, wherein the aryl and heteroaryl radicals may optionally besubstituted by halogen, C₁-C₆-alkyl, C₁-C₆-alkoxy, and/ortrimethylsilyl, and R¹ to R⁴, independently of one another, are eachhydrogen, C₁-C₁₀-alkyl, C₁-C₁₀-alkoxy, F, Cl, or Br, comprising (a)converting a phenol of the formula (II)

 in which R¹ to R⁴ have the meanings given for formula (I), into thecorresponding phenoxide using a base, (b) reacting the phenoxide withdihalogenomethane to give a formaldehyde acetal of the formula (III)

 in which R¹ to R⁴ have the meanings given for formula (I), (c)intramolecularly oxidatively coupling the formaldehyde acetal of theformula (III) is to give a cycloheptadiene of the formula (IV),

 in which R¹ to R⁴ have the meanings given for formula (I), (d)converting the cycloheptadiene of the formula (IV) by treatment with anacid into a biphenyldiol of the formula (V)

 in which R¹ to R⁴ have the meanings given for formula (I), (e)preparing the corresponding triflate from the biphenyldiol of theformula (V), and (f) coupling the triflate compound with a secondaryphosphine of the formula (VI) HPR₂  (VI),  in which R has the meaninggiven for formula (I),  with the addition of a base and in the presenceof a palladium(0), palladium(II), nickel(0), and/or Ni(II) compound,thereby giving a compound of the formula (I).
 2. A process for thepreparation of enantiomerically pure diphosphines of the formula (VIII)

in which the symbols used have the meanings given for formula (I), andof a formula that is analogous to formula (VIII) but represents theother enantiomer comprising carrying out the process of claim 1 andadditionally subjecting the biphenyldiol of the formula (V) to racemateresolution.
 3. Enantiomerically pure diphosphines of the formula (IX)

in which the radicals R″ are in each case identical and are 2-furyl,2-N-methylpyrrolyl, 4-fluorophenyl, 3,5-di-methoxyphenyl, or3,5-dimethylphenyl, and of a formula that is analogous to formula (IX)but represents the other enantiomer.
 4. A cycloheptadiene compound ofthe formula (IV)

where R¹ and R² are H, R³ is chlorine, and R⁴ is methoxy.
 5. Racemic andenantiomerically pure biphenyldiols of the formula (V)

and the corresponding racemic and enantiomerically pure triflatecompounds thereof, where R¹ and R² are H, R³ is chlorine, and R⁴ ismethoxy.
 6. A method of preparing a catalyst comprising combining ametal with a ligand comprising a racemic diphosphine prepared by theprocess according to claim
 1. 7. A method of preparing a catalystcomprising combining a metal with a ligand comprising anenantiomerically pure diphosphine prepared by the process according toclaim
 2. 8. A catalyst comprising a metal, metal ion, or metal complexof an element from subgroup VIII of the Periodic Table of the Elementsand at least one enantiomerically pure diphosphine according to claim 3as a ligand.
 9. A catalyst according to claim 8 wherein the element fromsubgroup VIII is ruthenium, iridium, or rhodium.
 10. A process accordingto claim 1 wherein R¹ and R² are hydrogen, R³ and R⁴ are C₁-C₄-alkoxy,fluorine, or chlorine, and R is phenyl, furyl, or2-N—C₁-C₆-alkylpyrrolyl, where phenyl, furyl, and2-N—C₁-C₆-alkylpyrrolyl may optionally be substituted by 1 to 3substituents selected from the group consisting of fluorine, chlorine,C₁-C₅-alkyl, C₁-C₅-alkoxy, and trimethylsilyl.
 11. A process accordingto claim 2 wherein R¹ and R² are hydrogen, R³ and R⁴ are C₁-C₄-alkoxy,fluorine, or chlorine, and R is phenyl, furyl, or2-N—C₁-C₆-alkylpyrrolyl, where phenyl, furyl and 2-N—C₁-C₆-alkylpyrrolylmay optionally be substituted by 1 to 3 substituents selected from thegroup consisting of fluorine, chlorine, C₁-C₅-alkyl, C₁-C₅-alkoxy, andtrimethylsilyl.
 12. A compound according to claim 4 wherein R¹ and R²are hydrogen and R³ and R⁴ are C₁-C₄-alkoxy, fluorine, or chlorine. 13.A compound according to claim 5 wherein R¹ and R² are hydrogen and R³and R⁴ are C₁-C₄-alkoxy, fluorine, or chlorine.
 14. A process accordingto claim 1 wherein (1) the phenol of the formula (II) is converted intothe corresponding phenoxide using an alkali metal hydride, hydroxide, orcarbonate at −20 to +60° C., (2) based on 1 mol of phenol of the formula(II) originally used, 0.4 to 0.7 mol of dihalogenomethane is reactedwith the phenoxide, (3) the formaldehyde acetal of the formula (III) isisolated from the reaction mixture following the addition of water usinga virtually nonpolar or nonpolar organic solvent, (4) for theintramolecular oxidative coupling for the preparation of thecycloheptadiene of the formula (IV), first an organolithium compound isadded at −30 to +40° C. and then a Cu(II), Fe(III), Mn(III) or Ce(IV)compound is added at −70 to −30° C., or the coupling is carried outenzymatically, (5) the treatment with an acid to convert thecycloheptadiene of the formula (IV) into a biphenyldiol of the formula(V) is carried out with 5 to 15 equivalents of a strong mineral acid,(6) for the preparation of the triflate compound, the biphenyldiol ofthe formula (V) is suspended in a solvent, and a tertiary amine and thentrifluoromethanesulfonic anhydride or trifluoromethanesulfonyl chlorideare added, and (7) the base used for the reaction of the triflatecompound with a secondary phosphine is a tertiary amine and ahydrogencarbonate.